Chem 6650 - from your list of reported scientific facts

Question

1. Literature interpretation.

(a) Find an article in the popular literature (e.g., newspaper, web, magazine, etc.) concerning some aspect of water chemistry that interests you.

(b) Read and dissect the article. Take note of that which is scientific fact, that which is an emotional statement, and that which is subjective (i.e an opinion or something in a person's mind that is unrelated to facts in the external world), or circumstantial. Make a list of what you perceive are the scientific, emotional, and circumstantial statements.

(c) From your list of reported scientific facts, write a short summary of the important chemistry that may be taking place.

(d) Speculate on the intent behind the article. For example, was it written to inform the reader about the science or induce concern or even fear over the issue and its consequences? Give evidence for your analysis from the list of scientific, emotional, and circumstantial statements.

(e) Point out any tendency for emotional statements concerning environmental issues that are beyond one's control.

(f) Finally, turn in your analysis, a copy of the article, and list any resources you used

2. Several different approaches have been proposed to sequester (or store) carbon dioxide to prevent additional global warming. Describe one of these methods (do some library or in-line research) with emphasis of the chemistry involved. What are the possible problems of the method if any?

3. Assume that you are on a planet whose atmosphere does not contain carbon dioxide, only nitrogen, oxygen, and water vapor.

(a) What would be the pH of the rain at 298K?

(b) Lets assume the alien life on the planet lives by eating sulfur and producing sulfur dioxide. If the atmospheric reaches a concentration of 20.0 ppmv of SO₂ what would the pH of the rain be at 298K and 1 atm. Use K_H for SO₂ = 1.12 M/atm and K_a= 1.7x10^-2 molL^-1

4. (a) Calculate the volume (at 20°C and 1.00 atm) of SO₂ produced by conventional roasting of 9.561 tonnes (9561 kg) of copper sulfide ore, CuS.

(b) What volume (in liters) of pure sulfuric acid (d= 1.8305 g/cm³) could be produced from this amount of SO₂ if it were oxidized to SO₃ and then reacted with water?

(c) The Apblett research group has developed a patent-pending method for converting sulfur dioxide to sulfur and sulfuric acid:

24 SO₂ + 16 H₂O → S₈ + 16 H₂SO₄

How much sulfur and how much sulfuric acid (in Kg) can be produced from the SO₂ according to part (a) of this question.

(d)   Look up the prices at Aldrich (either online or a recent chemical catalog) for sulfur and sulfuric acid (use prices for reagent grade material). Which process is more economical? Please show the pricing and your calculations in the answer.

5.   (A) If all of the ice on the planet were to melt it would produce 2.8 x 10⁷ km³ of water. The surface area of the ocean is 3.61 x 10⁸ km². Assuming that all of the water piled up on the top of the ocean and did not spread out, how large would the increase in sea height be (in meters)?

(B) Besides the assumption that the water does not spread out, what other factors may make this calculation incorrect. Hint: Consider the polar ice caps and icebergs and elementary school physics.

6.   The rate constant (k) for the reaction XH + OH• → X• + H₂O

Is 4.28 x 10^-5 molecules^-1cm³s^-1. If the atmospheric concentration of concentration of OH•  radical is 8.04 x 10 12 molecules cm^-3.

Calculate the half-life of XH.

7. If the concentration of atmospheric CO₂ were to double from its current level of 370 ppm, what would be the calculated pH of rainwater (assuming that CO₂ were the only acidic input)? With respect to rising CO₂ levels, do we have to be concerned about enhanced acidity of rain? See notes below for help with this calculation.

8. If the particle mass concentration on Hall of Fame in front of the construction area is 250 ug/m³, and the average particle size is 0.21 µm, what is the average number of particles/cc?  Assume a density of 0.98 g/ cm3 for the particles.

9. The rate constant for oxidation of nitric oxide by ozone is 2.4 x10^-14 cm³/molecule•s whereas that for the competing reaction where it is oxidized by oxygen is 2.3 x10^-38 cm³/molecule•s

2 NO + O₂ →2NO₂

In a typical morning smog condition the concentration of ozone is 42 ppb and that of NO is 78 ppb. Deduce the rates of the two oxidation reactions. Which one is the dominant process?

10. Assuming the enthalpy and entropy of formation of NO are temperature independent, what temperature (in Celsius) would be required to generate 88 ppmv of NO from the reaction of nitrogen and oxygen? Hint: Use thermodynamic data to calculate ?G with a correction for non-standard conditions for N₂, O₂, and. NO. The reaction will become thermodynamically possible when ?G=0. Assume atmospheric pressure of exactly 1 atmosphere and normal atmospheric concentrations of nitrogen and oxygen.

The hydration equilibrium constant at 25 °C is called Kh, which in the case of carbonic acid is [H₂CO₃]/[CO₂] ≈ 1.7×10^-3 in pure water. For carbonic acid, the K_a1 = 2.5×10^-4

pH and composition of carbonic acid solutions

At a given temperature, the composition of a pure carbonic acid solution (or of a pure CO₂ solution) is completely determined by the partial pressure pco₂ of carbon dioxide above the solution. To calculate this composition, account must be taken of the above equilibria between the three different carbonate forms (H₂CO₃, HCO₃^- and CO₃^2-) as well as of the hydration equilibrium between dissolved CO₂ and H₂CO₃ with constant K_h = [H₂CO₃]/[CO₂] (see above) and of the following equilibrium between the dissolved CO₂ and the gaseous CO₂ above the solution:

[CO₂] = CO₂(gas);=" CO₂(dissolved) with [CO₂]/PCO₂ = 1/k_H, where k_H = 29.76 atm/(mot/L) (Henry constant) at 25 °C.

The corresponding equilibrium equations together with the

[H⁺][OH^-] = 10^-14 relation and the charge neutrality condition

[H⁺] = [OH^-] + [HCO₃^-] + 2[CO₃^2-] result in six equations for the six unknowns [CO₂], [H₂CO₃], [H⁺],[OH^-], [HCO₃^-] and [CO3^2-], showing that the composition of the solution is fully determined by pCO₂ . The equation obtained for [H⁺] is a cubic whose numerical solution yields the following values for the pH and the different species concentrations

As noted above, [CO3^2-] may be neglected for this specific problem, resulting in the following very precise analytical expression for [H⁺]:

[H⁺] ≈ ( 10^-14 + K_hK_a1/k_HPCO₂)^1/2

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^{Please Answer Questions 3, 4, 5, 6, 7, 8, 9, 10, Do not need answer for 1 and 2.}